1. Field of the Invention
The present invention relates to a conveying system for continuous processing such as a pre-treatment of a semiconductor and to a control method of the system.
2. Description of the Related Art
FIG. 11 illustrates an example of a conventional pre-treatment conveying system for a semiconductor. As shown in the figure, the conveying system comprises a control computer 10 which controls the system as a whole, a terminal 11 disposed at each treatment area in a factory which is connected to the control computer 10, a depository 1 for storing a lot to be treated (including inspection), a plurality of treatment apparatuses 7 and 9, an in-process automated guided vehicle 5 moving between the treatment apparatuses, and inspection apparatuses 8.
The control computer 10 comprises a process information table having information for each process as shown in FIG. 8, and an apparatus information table having information for controlling conditions of each treatment apparatus as shown in FIG. 9. The process information table has information for each process, which apparatuses can process and processing conditions. The process information table also has information for each apparatus including an availability flag which shows whether the apparatus is available or not, a bay number which shows the location thereof, and a buffer number showing which locations can admit a lot.
The performance of the conventional conveying system will be described.
A lot comprising a plurality of untreated wafers is carried by the in-process automated guided vehicle 5 from the depository 1 to any of the treatment apparatuses 7 and 9 for treatment, under the control of instructions from the control computer 10. The flow of the lot after treatment will be described with reference to a flow chart in FIG. 10. When a treatment process of a lot is finished (S1), the control computer 10 retrieves apparatuses that can perform the next process (S2) and judges whether a free buffer is available in the apparatuses by referring to the apparatus information table (S4, S5) to decide the destination apparatus of the next process (S6). Then the control computer 10 instructs the in-process automated guided vehicle 5 to carry the lot to the instructed treatment apparatus (S8). On the other hand, since the inspection apparatus 8 is not included in the table information as an apparatus that can process, when the next process is inspection, the destination of the lot is set to be the depository 1 (S7).
An inspection operator selects the next lot to inspect from a plurality of lots waiting for inspection in the depository 1 by consulting the terminal 11, and takes the lot out of the depository 1. Then the lot is inspected at the inspection apparatus 8 and returned it to the depository 1 if it is acceptable. If it is not acceptable, it is carried to a storage for remedy or scrapping.
However, since in the conventional conveying system, as described above, all the completed lots waiting for inspection are carried into the depository 1, the following problems occur.
(1) An inspection operator has to perform bothersome operations such as retrieving lots in the depository by consulting the terminal 11, searching for the lots waiting for inspection among the lots retrieved, and selecting the next lot to be inspected. In order to eliminate these operations, when the lot waiting for inspection is put into the depository through an in-process gateway of the depository, it may be taken out automatically through an operator-gateway of the depository. However since the operator-gateway is constructed so that each lot is taken one-by-one, a lot which must be quickly inspected can not be taken out instantly. Consequently the problem is not solved effectively.
(2) Since the operator-gateway of the depository is used by not only inspection operators but also treatment apparatus operators, a lot can be mistaken.